AAS 201st Meeting, January, 2003
Session 77. The Interstellar Medium II
Poster, Wednesday, January 8, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[77.06] The Search for O2 with the Odin Satellite

M. Fich, C.L. Curry (University of Waterloo), L. Pagani (Observatoire de Paris), ODIN Team

Odin is a mm and submm heterodyne 1.1m radiotelescope mounted on a spacecraft launched on 20 February 2001. It has been developed in a partnership between Sweden, Canada, Finland and France. It is equipped with a 119 GHz HEMT amplifier and with 4 Schottky submm receivers in the range 486-580 GHz. All of the front-ends are mechanically cooled to 150 K. The antenna beam size is 9 arcmin at 119 GHz, the receiver tuning for the ground state transition of molecular oxygen. Its high sensitivity (SSB system temperature = 600 K) allows us to reach unprecedented upper limits on O2, especially in cold dark clouds where the 487 GHz line is not favorable to search for this species.

We will report on the latest results on our search for O2 with the Odin Satellite. In cold dark clouds we have already improved the published SWAS upper limits by an order of magnitude and reach O2/H2\le 10-7 in several sources. Goldsmith et al. (ApJ, in press) recently reported a SWAS tentative detection of 487 GHz O towards Oph A in a combination of 7 beams covering approximately 10 14 arcmin. In a brief (1.3 hour integration time) and partial coverage of the SWAS region ( 50% if we exclude the central position) we did not detect the corresponding 119 GHz line. Our 3 sigma upper limit on the O column density is 7.3\times 1015 cm-2. We presently cannot exclude the possibility that the SWAS signal lies mostly outside of our beam and escaped our sensitive detector. A better covering of the SWAS mapped region and deeper integration towards this source are planned to settle this question.

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